Nontuberculous mycobacterium (NTM) is a gram positive bacillus having acid-fast characteristics classified into genus Mycobacterium, and is a sort of acid-fast bacterium other than tuberculosis complex and Mycobacterium leprae.
Among nontuberculous mycobacterium, clinically problematic bacterial strain is known to include Mycobacterium kansasii, Mycobacterium marinum, Mycobacterium gordonae, Mycobacterium szulgai, Mycobacterium avium, Mycobacterium intracellulare, Mycobacterium xenopi, Mycobacterium fortuitum, Mycobacterium chelonei, Mycobacterium abscessus, and so on. Particularly, the infectious diseases affected by 2 types of bacteria, M. kansasii and M. avium complex, accounts 90% or more of the total nontuberculous mycobacterium diseases.
In general, the nontuberculous mycobacterium is said to be harmless to a healthy subject, however, on rare occasions, it may exert infectivity to human and causes nontuberculous mycobacterium diseases. Particularly in the immunocompromised subjects such as AIDS-virus-infected patients, it may be a serious infection-causative agent. In the past, the nontuberculous mycobacterium diseases have been rare disorder, however, in recent years, the incidence of infection demonstrates upward trend, and therefore, the development of a method for discriminating tuberculosis bacterium from nontuberculous mycobacterium in a short period of time has been desired strongly. Moreover, from the fact that the method for detecting/diagnosing M. avium and M. intracellulare by nucleic-acid amplification has been approved for its inclusion in health insurance coverage and then spread rapidly throughout the country, its diagnostic significance is obviously great.
Since most of nontuberculous mycobacteria have a resistance to antituberucular agents, when the patient is suspected of acid-fast bacterium infection, the differential diagnosis whether the disease is tuberculosis or nontuberculous mycobacterium disease will be quite important to decide on the course of treatment. In addition, as the method for the treatment of the diseases caused by nontuberculous mycobacteria may vary for each type of bacterium, the identification of bacterial species will also be quite important. However, since nontuberculous mycobacterium disease has no specific clinical symptom, it is quite difficult to differentiate tuberculosis from nontuberculous mycobacterium disease by clinical observation and histopathological manifestation, moreover, to specify the species of the nontuberculous mycobacterium. Therefore, the diagnosis whether the disease is tuberculosis or nontuberculous mycobacterium disease has to be performed by identification of the infected bacterium.
In a typical diagnosis, at first, sputum smear is examined. By this test, only “positive acid-fast bacterium” can be recognized, and differentiation of tuberculosis bacterium from nontuberculous mycobacterium cannot be achieved. Therefore, when the sputum smear examination is positive, bacterial culture examination by isolation culture on a specified culture medium such as Ogawa's medium is carried out to differentiate tuberculosis bacterium from nontuberculous mycobacterium. Further, through additional biochemical examinations, species of the bacterium is identified. However, in general, growth of bacterium belonging to genus Mycobacterium is slow, and takes considerable time for its culture. Accordingly, in the basic procedures of conventional method including smear examination and culture examination, it takes 3 to 4 weeks only for the isolation culture of the bacterium to obtain diagnostic outcome informing whether the bacterium is tuberculosis or not. In addition, there is another problem that it requires additional 2 to 3 weeks to complete various biochemical tests for the identification of bacterial species.
In addition, identification of M. kansasii is also performed by biochemical tests. The principal method of identifying M. kansasii by biochemical tests utilizes the specific property of producing pigment when the bacterium is exposed to the light. However, since some other species belonging to genus Mycobacterium show the same properties as M. kansasii shows, the identification of M. kansasii by its coloring property is generally of a problem.
In recent years, technology of detecting bacteria on a genetic level has been developed. For example, a diagnostic technique utilizing nucleic acid amplification technology such as polymerase chain reaction (PCR) and the like have been studied as a useful means. This method has advantages of high sensitivity; several cells of the bacteria are enough for the detection; detection can be completed in a short time (in 4 days at the longest). However, in the usual PCR method, both live cells and dead cells are detected equally. In addition, as the judgment is made positive regardless of the size of bacterial count, and since the number of the bacterium is unknown, diagnosis of infectivity whether it is positive or not will be provided with uncertainty. In addition, since the method has a problem that due to too high sensitivity, the possibility of false positive judgment or the like tends to be made.
As to M. kansasii, there is a study reporting that a DNA probe (pMK1-9) was obtained from genomic library of M. kansasii (Non-Patent Document 1). This DNA probe (PMK1-9) can form a complemental hybrid with the DNA of M. kansasii, but this probe can also form a hybrid with other species of mycobacteria, and is not specific to M. kansasii. 
Also, there is a study which paid attention to use of commercially available DNA probe (ACCU-PROBE™, GenProbe, San Diego, Calif.) which can hybridize specifically with pMK1-9 probe and rRNA gene of M. kansasii for the identification of M. kansasii (Non-Patent Document 2). However, in this study, it has been reported that both pMK1-9 probe and commercially available DNA probe (ACCU-PROBE™) were unable to detect considerable number of strain types of M. kansasii. 
Further, there is another study in which the commercially available DNA probe ACCU-PROBE™) was evaluated for the detection of M. kansasii (Non-Patent Document 3). The researchers of this study reported that although the ACCU-PROBE™ is 100% species specific, and does not show any cross reaction with other species of M. kansasii, only 73% of the species of M. kansasii could be detected in this experiment.
There is a report describing that a DNA hybrid forming probe (p6123) specific to M. kansasii has been purified from a clinical isolate of M. kansasii (Non-Patent Document 4). The probe (p6123) was able to hybridize with all the strains of M. kansasii used in this experiment including a sub-group which did not react with a DNA probe (pMK1-9) reported by Ross et al. U.S. Pat. No. 5,500,341 (Patent Document 2) has disclosed a M. kansasii-specific amplification primer purified from p6123 probe.
Further, B. Boddinghaus et al. have disclosed a Mycobacterium-specific oligonucleotide purified from 16S rRNA, which specifically proliferate and hybridize with mycobacterium DNA (Non-Patent Document 5).
Moreover, for example, identification of DNA region effective for detecting M. kansasii has also been studied (for example, Patent Document 1 and the like), however, the present situation is that the method of diagnosis specific to M. kansasii has not been established.
As described above, the present situation is that the establishment of a new specific method for detecting nontuberculous mycobacterium has been desired.    Patent Document 1: JP-A-11-155589;    Patent Document 2: U.S. Pat. No. 5,500,341;    Patent Document 3: JP-A-60-281;    Non-Patent Document 1: Z. H. Huang et. al., J. Clin. Microbiol., 1991, 29, p. 2125;    Non-Patent Document 2: B. C. Ross et al., J. Clin. Microbiol., 1992, 30, p. 2930;    Non-Patent Document 3: Tortoli et al., Eur. J. Clin. Microbiol. Infect. Dis., 1994, 13, p. 264;    Non-Patent Document 4: M. Yang et al., J. Clin. Microbiol., 1993, 31, p. 2769;    Non-Patent Document 5: B. Boddinghaus et al., J. Clin. Microbiol., 1990, 28, p. 1751;    Non-Patent Document 6: F. Poly et al., J. Bacteriology, 2004, 186, 14, p. 4781-4795.